Structure and chromosomal location of the rat gene encoding the heart fatty acid-binding protein

Tissue expression analysis, cloning and characterization of the 5'-regulatory region of the bovine FABP3 gene

Fatty acid binding protein 3 (FABP3) is a member of the FABP family which bind fatty acids and have an important role in fatty acid metabolism. A large number of studies have shown that the genetic polymorphisms of FABP3 are positively correlated with intramuscular fat (IMF) content in domestic animals, however, the function and transcriptional characteristics of FABP3 in cattle remain unclear. Real-time PCR analysis revealed that bovine FABP3 was highly expressed in cardiac tissue. The 5'-regulatory region of bovine FABP3 was cloned and its transcription initiation sites were identified. Sequence analysis showed that many transcriptional factor binding sites including TATA-box and CCAAT-box were present on the 5'-flanking region of bovine FABP3, and four CpG islands were found on nucleotides from -891 to +118. Seven serial deletion constructs of the 5'-regulatory region evaluated in dual-luciferase reporter assay indicated that its core promoter was 384 base pairs upstream from the transcription initiation site. The transcriptional factor binding sites RXRα, KLF15, CREB and Sp1 were conserved in the core promoter of cattle, sheep, pigs and dogs. These results provide further understanding of the function and regulation mechanism of bovine FABP3.

The fabp4 gene of zebrafish (Danio rerio)--genomic homology with the mammalian FABP4 and divergence from the zebrafish fabp3 in developmental expression

Teleost fishes differ from mammals in their fat deposition and distribution. The gene for adipocyte-type fatty acid-binding protein (A-FABP or FABP4) has not been identified thus far in fishes. We have determined the cDNA sequence and defined the structure of a fatty acid-binding protein gene (designated fabp4) from the zebrafish genome. The polypeptide sequence encoded by zebrafish fabp4 showed highest identity to the H(ad)-FABP or H6-FABP from Antarctic fishes and the putative orthologs from other teleost fishes (83-88%). Phylogenetic analysis clustered the zebrafish FABP4 with all Antarctic fish H6-FABPs and putative FABP4s from other fishes in a single clade, and then with the mammalian FABP4s in an extended clade. Zebrafish fabp4 was assigned to linkage group 19 at a distinct locus from fabp3. A number of closely linked syntenic genes surrounding the zebrafish fabp4 locus were found to be conserved with human FABP4. The zebrafish fabp4 transcripts showed sequential distribution in the developing eye, diencephalon and brain vascular system, from the middle somitogenesis stage to 48 h postfertilization, whereas fabp3 mRNA was located widely in the embryonic and/or larval central nervous system, retina, myotomes, pancreas and liver from middle somitogenesis to 5 days postfertilization. Differentiation in developmental regulation of zebrafish fabp4 and fabp3 gene transcription suggests distinct functions for these two paralogous genes in vertebrate development.

The multigene family of fatty acid-binding proteins (FABPs): function, structure and polymorphism

Fatty acid-binding proteins (FABPs) are members of the superfamily of lipid-binding proteins (LBP). So far 9 different FABPs, with tissue-specific distribution, have been identified: L (liver), I (intestinal), H (muscle and heart), A (adipocyte), E (epidermal), Il (ileal), B (brain), M (myelin) and T (testis). The primary role of all the FABP family members is regulation of fatty acid uptake and intracellular transport. The structure of all FABPs is similar - the basic motif characterizing these proteins is beta-barrel, and a single ligand (e.g. a fatty acid, cholesterol, or retinoid) is bound in its internal water-filled cavity. Despite the wide variance in the protein sequence, the gene structure is identical. The FABP genes consist of 4 exons and 3 introns and a few of them are located in the same chromosomal region. For example, A-FABP, E-FABP and M-FABP create a gene cluster. Because of their physiological properties some FABP genes were tested in order to identify mutations altering lipid metabolism. Furthermore, the porcine A-FABP and H-FABP were studied as candidate genes with major effect on fatness traits.

Structure, linkage mapping and expression of the heart-type fatty acid-binding protein gene (fabp3 ) from zebrafish (Danio rerio)

We have determined the cDNA nucleotide sequence, deduced the amino acid sequence and defined the gene structure for the cellular heart-type (H-FABP) or fatty acid-binding protein 3 (FABP3) from zebrafish. The zebrafish FABP3 exhibited the greatest amino acid sequence identity to fish and mammalian heart-type FABPs. 3' RACE and 5' RLM-RACE mapped two alternative polyadenylation sites and three transcription start sites, respectively. Southern blot and hybridization analysis indicated that a single fabp3 gene exists in the zebrafish genome. The zebrafish fabp3 gene consists of four exons interrupted by three introns with identical exon/intron structure and coding capacity with that of orthologous mammalian H-FABP genes. Radiation hybrid mapping assigned the zebrafish fabp3 gene to linkage group 19 of the zebrafish genome. Comparative genomic analysis revealed conserved syntenies of the zebrafish fabp3 gene and the orthologous human and mouse fabp3 genes. Northern blot analysis detected an mRNA transcript of 780 nucleotides. In situ hybridization of the zebrafish fabp3-specific oligonucleotide probe to tissue sections of adult zebrafish revealed that the fabp3 mRNA was localized in the ovary and liver, but not in the heart, muscle or brain as reported for the mammalian fabp3 gene transcript. RT-PCR, however, detected zebrafish fabp3 mRNA in all the tissues examined. Emulsion autoradiography further revealed that the zebrafish fabp3 mRNA was most abundant in primary growth stage (stage I) oocytes and decreased during the oocyte growth phase. The fabp3 mRNA levels were reduced and restricted to the ooplasm of cortical alveolus stage (stage II) oocytes, and nearly undetectable in stage III and matured oocytes. Inspection of the 5' upstream sequence of the zebrafish fabp3 gene revealed a number of cis elements that may be involved in the expression of the zebrafish fabp3 gene in oocytes and liver.

A novel fatty acid response element controls the expression of the flight muscle FABP gene of the desert locust, Schistocerca gregaria

In many tissues, fatty acid binding protein (FABP) expression is stimulated by exposure to elevated fatty acid levels. In contrast to the FABP genes expressed in other tissues, the molecular mechanisms that mediate the upregulation of the muscle FABP gene have not been elucidated. We have studied the expression of locust flight muscle FABP, a protein that is highly homologous to the mammalian H-FABPs. A 130-bp promoter fragment of the locust gene, which includes a canonical TATA box and several GC boxes, is sufficient for the transcription of a reporter gene in mammalian L6 myoblasts. Twofold higher expression rates are observed when the promoter contains 280 bp or more of upstream sequence. Treatment of myoblasts with various fatty acids leads to a marked increase of expression in the longer constructs, but not in the minimal promoter. We have identified a 19-bp inverted repeat (-162/-180) as the element responsible for the fatty acid-mediated induction of gene expression. Deletion of this element eliminates the fatty acid response, and gel shift analysis demonstrates specific binding to nuclear proteins from both L6 myoblasts and locust flight muscle cells. This fatty acid response element bears no similarity to any known transcription factor binding site. A similar palindrome was also found in the promoter of the Drosophila melanogaster muscle FABP gene, and in reverse orientation upstream of all mammalian heart FABP genes. Given the structural and functional conservation of muscle FABPs and their genes, it is possible that this fatty acid response element also modulates the expression of the mammalian H-FABP genes.

Induction of cardiac FABP gene expression by long chain fatty acids in cultured rat muscle cells

The induction of cardiac FABP expression by long-chain fatty acids was measured in cultured rat myoblasts, myotubes and adult cardiomyocytes. With quantitative RT-PCR techniques, the primary transcription product of the FABP gene and the mature mRNA were measured. Incubations of 30 min resulted in a larger than 2-fold increase of the primary transcript in all cells, and FABP mRNA more than doubled in myoblasts and cardiomyocytes after 10 h of fatty acid exposure. The results demonstrate that long chain fatty acids induce the expression of the cardiac FABP gene in muscle cells and their undifferentiated precursors at the level of transcription initiation, suggesting that all factors involved in fatty acid dependent gene induction are already present in myoblasts. Thus, myoblast cell lines should be useful for the characterization of fatty acid response elements that control the expression of the FABP gene.

Cloning and sequence of the gene encoding the muscle fatty acid binding protein from the desert locust, Schistocerca gregaria

Muscle fatty acid binding protein (FABP) is a major cytosolic protein in flight muscle of the desert locust, Schistocerca gregaria. FABP expression varies greatly during development and periods of increased fatty acid utilization, but the molecular mechanisms that regulate its expression are not known. In this study, the gene coding for locust muscle FABP was amplified by PCR and cloned, together with 1.2 kb of upstream sequence. The sequence coding for the 607 bp cDNA is interrupted by two introns of 12.7 and 2.9 kb, inserted in analogous positions as the first and third intron of the mammalian homologues. Both introns contain repetitive sequences also found in other locust genes, and the second intron contains a GT-microsatellite. The promoter sequence includes a canonical TATA box 24 bp upstream of the transcription start site. The upstream sequence contains various potential myocyte enhancer sequences and a 160 bp segment that is repeated three times. In database searches in the genome database of Drosophila melanogaster, a gene with the same gene organization and promoter structure was identified, likely the dipteran homologue of muscle FABP. Upstream of both insect genes, a conserved 19 bp inverted repeat sequence was detected. A similar but reverse palindrome is also present upstream of all mammalian heart FABP genes, possibly representing a novel element involved in muscle FABP expression.

Gene targets related to phospholipid and fatty acid metabolism in schizophrenia and other psychiatric disorders: an update

Phospholipids make up about 60% of the brain's dry weight and play key roles in many brain signal tranduction mechanisms. A recent review(1)identified the increasing evidence that abnormal phospholipid and related fatty acid metabolism may contribute to illnesses such as schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder. This current paper reviews the main pathways of phospholipid metabolism, emphasizing the role of phospholipases of the A2 in signal tranduction processes. It also updates the chromosomal locations of regions likely to be involved in these disorders, and relates these to the known locations of genes directly or indirectly involved in phospholipid and fatty acid metabolism.